I’ve had CNAME Flattening set to “Flatten all CNAMEs” for the performance boost since a couple of my subdomains unfortunately have a chain of CNAMEs to resolve.
I recently signed up with a new email API and for deliverability they need a CNAME record set for the return path of all outgoing messages. I made sure to set the cloud icon to grey (not proxied) and yet their config pages still wouldn’t OK my DNS setup. I tried changing the CNAME flattening setting to only “Flatten CNAME at root” and then everything was approved by the email service.
I presumed that with the grey cloud icon the DNS entry would just work like a “normal” one with any other DNS service, but if you switched this to orange then “Cloudflare would apply” and stuff like CNAME flattening would take place?
I did read through the blog post where CF launched CNAME flattening but it doesn’t seem to address this. I also only have a Pro account so maybe there is more control if you have Business/Enterprise?
Also, not trying to be snarky, but if a CNAME record just returns the string set in it - what is the difference between a CNAME record with the orange cloud and with the grey cloud? Both would just return the same string? Maybe there is something I don’t understand re: CNAMEs.